EP2384816B1

EP2384816B1 - Method of manufacturing a nanochannel device

Info

Publication number: EP2384816B1
Application number: EP11164603.0A
Authority: EP
Inventors: Gang Wang; Joshua Tseng; Roger Loo
Original assignee: Interuniversitair Microelektronica Centrum vzw IMEC; KU Leuven Research and Development; Taiwan Semiconductor Manufacturing Co TSMC Ltd
Current assignee: Interuniversitair Microelektronica Centrum vzw IMEC; KU Leuven Research and Development; Taiwan Semiconductor Manufacturing Co TSMC Ltd
Priority date: 2010-05-04
Filing date: 2011-05-03
Publication date: 2018-04-04
Anticipated expiration: 2031-05-03
Also published as: EP2384816A1; US20110272789A1; JP6009738B2; US8384195B2; JP2012023337A

Description

TECHNICAL FIELD OF THE DISCLOSURE

The present invention relates to a method for manufacturing said nanochannel device.
The method can for example be used or integrated in high throughput and low cost manufacturing such as the ultra-large scale integration semiconductor manufacturing.

BACKGROUND OF THE INVENTION

Manipulating matter at the nanometer scale is important for many electronic, chemical and biological advanced applications, but present solid-state fabrication methods do not reproducibly achieve dimensional control at the nanometer scale.
For example, nanochannels or nanopores with pore width (or channel width) of less than 10nm are of great interest in single molecule or DNA separation and detection.
High throughput, low cost and precise diameter and length control are needed in bioMEMS, biochips and biosensors. In addition, easy integration approach for nanochannel fabrication with device processing is required.
Conventional approaches for forming nanochannels are e-beam lithography and ion-beam sculpting, both known to be expensive and highly complex.
Alternatively, a sequence of oxidation and CMP is a well established technique, with a high process complexity, capable to fabricate pores with large diameter.
Depositing a non-conformal PECVD film is also a well established process suitable for forming pores having a large diameter, but having unfortunately process control issues and requiring thermal treatments upon deposition. Examples are further known from WO03/010289 , which discloses nanosized trenches in a silicon substrate that are sealed with silicon dioxide to leave nanochannels in the center of the trenches, and from US2008/036030 , in which microsized trenches in a silicon substrate are closed by epitaxial growth of silicon, leaving micro channels in the center of the trenches.
In conclusion, these conventional approaches are either expensive or they show poor control over the size (width and length) and uniformity of nanochannel. Some conventional fabrication approaches are not integration friendly, either.

AIMS OF THE INVENTION

It is an aim of the present invention to provide a nanochannel device comprising an embedded nanochannel (or nanopore) having a (channel or pore) width smaller than 1 micron, preferably smaller than 10 nm, and a (channel or pore) length in the microns range or longer.
More particularly, it is an aim of the present invention to provide a nanochannel device comprising an embedded nanochannel (or nanopore) having a (substantially) uniform width over the whole length of said nanochannel.
Furthermore, the present invention is aimed at providing a nanochannel device comprising an array of nanochannels having a regular distribution of nanochannels, each of the nanochannels having a width smaller than 1 micron, preferably smaller than 10nm, a (channel or pore) length in the microns range or longer, and having a (substantially) uniform width over the whole length of each of said nanochannels.
Yet another aim of the present invention is to provide a method for manufacturing said nanochannel device comprising an embedded nanochannel or array of nanochannels.

SUMMARY OF THE INVENTION

The present invention concerns a method for manufacturing a nanochannel device, according to claim 1. A device made using the method according to the present invention can be described as a device comprising a mono-crystalline substrate the monocrystalline substrate having at least one recessed region which exposes predetermined crystallographic planes of the mono-crystalline substrate, the at least one recessed region further having a recess width and comprising a filling material and an embedded nanochannel, wherein a width, a shape and a depth of the embedded nanochannel is determined by the recess width of the at least one recessed region and by a growth rate of a growth front of the filling material in a direction perpendicular to the predetermined crystallographic planes exposed.
The device of the above, may comprise multiple recessed regions, each recessed region comprising an embedded nanochannel.
In the device of the above, the embedded nanochannels may form an array.
In the device of any of the above, the width of the embedded nanochannel is lower or equal than (about) 1 micron.
In the device of any of the above, wherein the width of the embedded nanochannel may be lower or equal than (about) 10 nm.
In the device of any of the above, the filling material is germanium (Ge).
In the device of any of the above, the filling material may further comprise oxygen, nitrogen and/or carbon.
The method according to the present invention is defined by claim 1.
Preferably, a width, a shape and a depth of the embedded nanochannel is determined by the recess width of the recessed region and the growth rate of the growth front of the filling material in the direction perpendicular to the predetermined crystallographic planes exposed.
Preferably, no thermal treatment is performed prior to forming the embedded nanochannel.
Preferably, the epitaxial deposition method is suitable to control the growth rates of the growth fronts of the filling material in different directions perpendicular to the exposed crystallographic planes, independently of each other.
Preferably, the epitaxial deposition method is selected from chemical vapor deposition (CVD) and molecular beam epitaxy (MBE).
The width of the embedded nanochannel is lower than (about) 1 micron. Preferably, the width of the embedded nanochannel is lower than (about) 10 nm.
Using the method of the present invention, a nanochannel device comprising an embedded nanochannel (or nanopore) having a ((substantially) uniform) width smaller than (about) 1 micron, preferably smaller than (about) 10 nm, and a (channel or pore) length in the microns range or longer can be manufactured.
Furthermore, using the method of the present invention, a nanochannel device comprising an array of nanochannels, said array comprising a regular distribution of nanochannels can be manufactured. Each of the nanochannels in said array in said device having a ((substantially) uniform) width smaller than (about) 1 micron, preferably smaller than (about) 10 nm.
The present invention also provides a method for manufacturing an embedded nanochannel or array of nanochannels having a ((substantially) uniform) width smaller than (about) 1 micron, preferably smaller than (about) 10 nm, and a length in the range of microns or longer, using an epitaxial deposition method compatible with the semiconductor manufacturing.
The method of the present invention has the advantage over existing methods in prior art that said fabricated nanochannel device comprises a nanochannel, or array of nanochannels, with controlled nanochannel size, width, and length (i.e. dimensional control at nanometer scale), said width being (substantially) uniform over the whole length of said nanochannel(s).
It is an advantage of the present invention over existing methods in prior art that the dimensions or size (width and length) and uniformity of the nanochannel is controlled.
In other words, it is an advantage of the present invention over prior art that the width of the nanochannel(s) is uniform over the whole length of said nanochannel(s).
Furthermore, the method of the invention provides the advantage that a nanochannel device comprising a nanochannel, or array of nanochannels, having a ((substantially) uniform) nanochannel width between (about) 0.5 nm and (about) 1 micron, more preferably between (about) 1 nm and (about) 20 nm, and even more preferably between (about) 5 nm and (about) 10nm, can be manufactured in a reproducible and controllable manner.
The method of the invention can for example be used (or implemented, or integrated) in high throughput and low cost manufacturing, such as ultra-large scale integration semiconductor manufacturing.
The method of the present invention has the advantage over existing methods in prior art that it is a simplified (being less complex), low cost, and easy to control, method.
It is an advantage of the method of the invention, compared to methods for forming nanochannels described in the art, that no thermal treatment is performed or required prior to forming the embedded nanochannel.
It is an advantage of the method of the invention, compared to methods for forming nanochannels described in the art, that no chemical-mechanical processing or polishing (CMP) is required (and that a CMP step is even avoided).
Using the method of the present invention, a device can be manufactured comprising (or consisting of) a mono-crystalline substrate, the mono-crystalline substrate having (or comprising, or consisting of) at least one recessed region (or recess, or trench) which exposes predetermined crystallographic planes of the mono-crystalline substrate, the at least one recessed region (or recess, or trench) further having a recess (or trench) width and comprising a filling material and an embedded nanochannel (or nanopore), wherein the width, the shape, and the depth of the embedded nanochannel (or nanopore) is determined by the recess (or trench) width of the at least one recessed region (or recess, or trench) and by the growth rate of the growth front (or plane) of the filling material in a direction perpendicular to the exposed predetermined crystallographic planes.
In the context of the present invention, a "mono-crystalline substrate" refers to a mono-crystalline semiconductor substrate per se, or a mono-crystalline epitaxial semiconductor layer formed on a suitable (mono-crystalline or poly-crystalline) semiconductor substrate.
In the method according to the invention a mono-crystalline silicon (Si) substrate is used.
In the context of the present invention, a "recessed region" refers to a recess, or a trench.
In the context of the present invention, "an embedded nanochannel (or nanopore)" is a nanochannel (or nanopore) which is completely surrounded by the filling material.
In the context of the present invention, the "width of a nanochannel" (w_c) (as illustrated in Figure 2) refers to the diameter of the nanochannel in case of a circular cross-section. In case the cross-section of the nanochannel has another regular shape (e.g. diamond-like, a square, a rectangle, a hexagon, a triangle), the width of a nanochannel refers to the double of the distance from its center, or axis of symmetry, to a point in the periphery, usually the point farthest from the center or axis (outermost radius r). Without wishing to be bound by theory, it is believed that this radius r, equal to the half of the channel width w_c, can be expressed by the formula: $r = w [\frac{1}{2 \sin θ_{111} \cos θ_{111}} - \frac{G R^{111}}{2 G R^{110} \cos θ_{111}}]$
wherein w is the recess width, GR¹¹¹ and GR¹¹⁰ the growth rate of the growth front (or plane) perpendicular to the {111} and {110} crystallographic plane respectively, and θ₁₁₁ the angle between the {111} crystallographic plane and the horizontal plane (or bottom of the recess region).
The shape of the embedded nanochannel (or nanopore) in the device according to the invention can be diamond-like, round, square, triangle, rectangle, or hexagonal.
In the context of the present invention, the "depth of a channel" (z_c) (as illustrated in Figure 2) refers to the distance between the bottom of the channel and the bottom of the recess. The depth of the channel depends on the recess width (w) and the ratio between the growth rate GR⁰⁰¹ of the growth front (or plane) perpendicular to the {001} crystallographic plane (or growth rate GR¹⁰⁰ of the growth front (or plane) perpendicular to the {100} crystallographic plane) and the growth rate GR¹¹⁰ of the growth front (or plane) perpendicular to the {110} crystallographic plane, as illustrated by the formula: $z_{c} \approx \frac{w}{2} \frac{G R^{001}}{G R^{110}}$
Preferably, the device manufactured using the method according to the invention, comprises (or consists of) multiple recessed regions (or recesses, or trenches), each recessed region comprising (or consisting of) an embedded nanochannel.
More preferably, in the device manufactured using the method according to the invention, the embedded nanochannels form an array or a network of nanochannels (said array or network of nanochannels comprising a regular distribution of nanochannels).
More particularly, said nanochannels of said array or network may be inter-connected or not.
In the device manufactured using the method according to the invention, the width of the embedded nanochannel is lower than or equal to (about) 1 micron, preferably lower than or equal to (about) 10 nm.
More particularly, the width of the embedded nanochannels is comprised between (about) 0.5 nm and (about) 1 micron, more preferably between (about) 1 nm and (about) 20 nm, and even more preferably between (about) 5 nm and (about) 10nm.
Preferably, in the device manufactured using the method according to the invention, the length of the embedded nanochannel is (about) 100 nm or more.
Preferably, in the device manufactured using the method according to the invention, the width of the embedded nanochannel is (substantially) uniform over the whole length of said embedded nanochannel.
In the context of the present invention, a "(substantially) uniform width of the embedded nanochannel over the whole length of said embedded nanochannel" refers to a width of the embedded nanochannel being (substantially) the same over the whole length of said embedded nanochannel.
Preferably, in the device manufactured using the method according to the invention, the embedded nanochannel is horizontal.
In the context of the present invention, a "horizontal (embedded) nanochannel" refers to a (embedded) nanochannel having its longest dimension (or length) in a horizontal direction (i.e. horizontal or parallel with respect to the bottom (plane) of the recess region).
In the device manufactured using the method according to the invention, the filling material (or the material wherein the nanochannel is embedded) can be any material suitable to be (selectively and conformal) grown epitaxially and (directly) in a pre-defined (or pre-etched) recess (or recessed region, or trench).
In the method according to the present invention the filling material is germanium (Ge).
Preferably, the filling material further comprises oxygen, nitrogen, and/or carbon.
More particularly, the filling material may be further treated to form oxides, nitrides, or carbides of said filling material.
Preferably, in the method of the invention, said at least one recessed region (or recess, or trench) (having a recess width and recess depth) is formed in said substrate by a patterning process (or lithography and etching process).
Preferably, in the method of the invention, the filling material is only (or selectively) formed (directly) in (or inside) the at least one recessed region (or recess, or trench).
Preferably, in the method of the invention, no chemical-mechanical processing (or chemical-mechanical polishing, or CMP) step is performed (or in other words, in the method of the invention, a CMP step is avoided).
Preferably, in the method of the invention, said growth rate is controlled by introducing chloride during said epitaxial growth.
A suitable amount of chloride for use in a method according to the invention depends on the recess width and recess depth of the at least one recessed region (or recess, or trench).
Finding a suitable amount of chloride for use in a method according to the invention is well within the practice of those skilled in the art.
More preferably, HCl is introduced during said epitaxial growth.
In a method of the invention, the shape of the (embedded) nanochannel can be modified (e.g. rounded) by a thermal treatment.
More preferably, in the method of the invention, said epitaxial growth is performed at atmospheric pressure, and at a temperature between (about) 250°C and (about) 600°C, more preferably between (about) 350°C and (about) 600°C (for (further) shaping the nanochannel).
Preferably, in the method of the invention, the width, the shape and the depth of the embedded nanochannel is determined by the recess width of the at least one recessed region and by the growth rate of the growth front of the filling material in the direction perpendicular to the exposed predetermined crystallographic planes.
Preferably, in the method of the invention, no thermal treatment is performed prior to (the step of) forming the embedded nanochannel.
Preferably, in the method of the invention, the epitaxial growth of the filling material is suitable to control the growth rates of the growth fronts of the filling material in different directions perpendicular to the exposed crystallographic planes, independently of each other.
More particularly, the epitaxial growth of the filling material is performed by chemical vapor deposition (CVD), or molecular beam epitaxy (MBE).
In the method of the invention, the filling material (or the material wherein the nanochannel is embedded) can be any material suitable to be (selectively and conformal) grown epitaxially and (directly) in a pre-defined (or pre-etched) recess (or recessed region, or trench).
Preferably, in the method of the invention, the width of the embedded nanochannel is lower than or equal to (about) 1 micron, preferably lower than or equal to (about) 10 nm.
More particularly, the width of the embedded nanochannels is comprised between (about) 0.5 nm and (about) 1 micron, more preferably between (about) 1 nm and (about) 20 nm, and even more preferably between (about) 5 nm and (about) 10nm.
Advantageously, the width of the embedded nanochannel is (substantially) uniform over the whole length of said embedded nanochannel.
More preferably, the embedded nanochannel is horizontal.
According to the method of the invention, the mono-crystalline substrate is a silicon substrate having a {100} orientation and at least one recessed region, said recessed region exposing the {100}, {110}, and {111} crystallographic planes of the silicon substrate, wherein the filling material is germanium and wherein the growth rate of the growth front of germanium in a direction perpendicular to the exposed {110}, {100}, and {111} crystallographic plane is controlled such that an embedded nanochannel is formed in said at least one recessed region at an intersection of said growth fronts of germanium.
More preferably, said growth rate is controlled by introducing chloride during said epitaxial growth.
Even more preferably, HCl is introduced during said epitaxial growth.
More preferably, chloride is introduced during the epitaxial growth for reducing the growth rate of the growth front of germanium in a direction perpendicular to the exposed {100} crystallographic plane more than the growth rate of the growth front of germanium in a direction perpendicular to the exposed {110} crystallographic plane, thereby forming {111} facets before two (opposite) {110} crystallographic planes merge.
In the context of the present invention, two opposite {110} crystallographic planes refer to two {110} crystallographic planes being opposite with respect to the z-axis (or being on opposite sides of the z-axis, or facing each other) as depicted in figure 2.
Even more preferably, the formation of {111} facets maintain the uniformity of pore diameter or width along the whole length of the nanochannel.
More preferably, said epitaxial growth is performed at atmospheric pressure, and at a temperature between (about) 250°C and (about) 600°C, more preferably between (about) 350°C and (about) 600°C (for (further) shaping the nanochannel), thereby forming an embedded nanochannel with a rectangular shape in said at least one recessed region at an intersection of said growth fronts of
A device manufactured using the method of the present invention can be part of (or integrated with) bio-microelectromechanical systems (bioMEMS), biochips, biosensors, or micro fluidic devices.
The nanochannels of the device manufactured using the method of the present invention can be used (or are suitable) for single molecule or DNA separation and/or detection (with nanochannel widths of less than (about) 10 nm).

SHORT DESCRIPTION OF THE DRAWINGS

All drawings are intended to illustrate some aspects and embodiments of the present disclosure. The drawings described are only schematic and are non-limiting.

Fig. 1(a) represents a Transmission Electron Microscopy (TEM) picture of a nanochannel with a width less than 10 nm.
Fig 1(b) represents a TEM picture of a nanochannel in the Y-Y direction (depicted in Fig. 1(a)) showing a channel length of more than 100 nm.
Fig. 2 represents schematically the evolution of the epitaxial growth and the forming of the nanochannel.
Fig. 3 represents schematically the manufacturing flow according to an embodiment of the disclosure.

DESCRIPTION OF THE INVENTION

An aim of the present disclosure is to provide (a nanochannel device comprising) an embedded nanochannel (or nanopore) having a (channel or pore) width smaller than 1 micron and a (channel or pore) length in the microns range or longer.
Preferably the width/diameter of the nanochannel is (substantially) uniform over the whole length.
More preferably the width/diameter is smaller than 10nm.
Another aim is to provide (a nanochannel device comprising) an array of nanochannels comprising a regular distribution of nanochannels, each of the nanochannels having a diameter smaller than 1 micron, more preferably smaller than 10nm and a good (or high) uniformity over the whole length (when compared to devices in the art).
Yet another aim is to provide a method to manufacture (a nanochannel device comprising) an embedded nanochannel or array of nanochannels having diameter smaller than 1 micron, more preferably smaller than 10nm and a length in the range of microns or longer using an epitaxial deposition method compatible with the semiconductor manufacturing.
Preferably the method has higher throughput and/or lower costs compared with the state in the art methods.
In one aspect of the present disclosure a device is disclosed, comprising (or consisting of) a mono-crystalline substrate, the monocrystalline substrate having at least one recessed region which exposes predetermined crystallographic planes of the mono-crystalline substrate, the at least one recessed region further having a recess width and comprising (or consisting of) a filling material and an embedded nanochannel (a nanochannel which is completely surrounded by the filling material), wherein a width and a shape of the embedded nanochannel is determined by the recess width of the at least one recessed region and by a growth rate of a growth front of the filling material in a direction perpendicular to the predetermined crystallographic planes exposed.
It is an advantage of the disclosed device to have an adjustable nanochannel width and nanochannel length.
Alternatively or additionally a good (or high) uniformity in nanochannel width/diameter is obtained over the whole length (when compared to devices in the art).
A device made using the method according to embodiments of the present invention comprises (or consists of) multiple recessed regions, each recessed region comprising (or consisting of) a nanochannel.
Further, the nanochannels may form an array or a network of nanochannels which can be inter-connected or not.
The width of the nanochannel is (substantially) uniform over the whole length and lower or equal than 1 micron.
An embedded nanochannel with a uniform width lower or equal than 10nm is another advantage of the present disclosure.
Nanochannels having a width (diameter) between 1 micron and 0.5 nm, more preferably between 1nm and 20 nm and even more preferably between 5 nm and 10nm can be manufactured in a reproducible and controllable manner.
According to the invention, the filling material or the material wherein the nanochannel is embedded is germanium (Ge).
According to further embodiments of the disclosure the filling material can further comprise (or consist of) oxygen, nitrogen, carbon.
The method for manufacturing a nanochannel device according to the invention is defined in claim 1.
Throughout the disclosure, by an embedded nanochannel is understood a nanochannel completely surrounded by a filling material.
Different embodiments further disclose that a width and a shape of the nanochannel is determined by the recess width of the recessed region and the growth rate of the growth front of the filling material in the direction perpendicular to the predetermined crystallographic planes exposed.
The depth of the channel (z_c) as illustrated in Figure 2 is defined as the distance between the bottom of the channel and the bottom of the recess and depends on the recess width (w) and the ratio between the growth rate GR⁰⁰¹ of the growth front (or plane) perpendicular to the (001) crystallographic plane and the growth rate (GR¹¹⁰) of the growth front (or plane) perpendicular to the {110} crystallographic plane, as illustrated by formula below. $z_{c} \approx \frac{w}{2} \frac{G R^{001}}{G R^{110}}$
Throughout the disclosure, the width of the nanochannel (w_c) (as illustrated in Figure 2) is to be understood as the diameter of the nanochannel in case of a circular cross-section. In case the cross-section of the nanochannel has another regular shape, (e.g. diamond-like, a square, a rectangle, a hexagon, a triangle) the width of the nanochannel refers to the double of the distance from its center, or axis of symmetry, to a point in the periphery, usually the point farthest from the center or axis (outermost radius r). Without willing to be bound by theory, this radius r, equal to the half of the channel width w_c, can be expressed by the following formula: $r = w [\frac{1}{2 \sin θ_{111} \cos θ_{111}} - \frac{G R^{111}}{2 G R^{110} \cos θ_{111}}]$
wherein w is the recess width, GR¹¹¹ and GR¹¹⁰ the growth rate of the growth front perpendicular to the {111} and respectively {110} crystallographic plane, and θ₁₁₁ the angle between the {111} crystallographic plane and the horizontal plane (bottom of the recess region).
It is an advantage of the method that no thermal treatment is performed or required prior to forming the embedded nanochannel.
The epitaxial deposition method is suitable to control the growth rates of the growth fronts of the filling material in different directions perpendicular to the exposed crystallographic planes, independently of each other.
In specific embodiments, the epitaxial deposition method is selected from chemical vapor deposition (CVD) and molecular beam epitaxy (MBE).
The method according to the invention comprises (or consists of):

providing a silicon substrate having a (100) orientation and at least one recess, said recess exposing the {110} and {111} crystallographic planes the silicon substrate, and
epitaxially growing germanium in the recess, wherein a growth rate of a growth front of germanium in a direction perpendicular to the exposed {110}, {100} and, respectively, {111} crystallographic plane exposed are controlled such that a nanochannel with a rectangular shape is formed at an intersection of said growth fronts of germanium.

The growth rates of the growth fronts of germanium in a direction perpendicular to the exposed {110}, {100} and {111} crystallographic planes are controlled by supplying a controlled amount of precursor (e.g. GeH₄, Ge₂H₆, Ge₃H₈) and HCl at certain temperature and pressure conditions.
In the context of the present invention, the term "precursor" refers to molecules used for forming (or depositing) the (semiconductor) filling material in (or inside) the at least one recessed region (or recess, or trench).
A suitable precursor for use in a method according to the invention depends on the filling material to be deposited in (or inside) the at least one recessed region (or recess, or trench).
Examples of precursors suitable for use in a method of the invention are germanium precursors (germane, digermane, trigermane, or any other high order germanium precursors).
Finding a suitable (amount of) precursor for use in the method of the invention will be apparent to those skilled in the art.
A suitable amount of chloride for use in a method according to the invention depends on the recess width and recess depth of the at least one recessed region (or recess, or trench).
In a method of the invention, a flow of chloride (e.g. HCl, or Cl₂) is chosen to have a balance between the growth rates on all exposed predetermined crystallographic planes of the at least one recessed region (or on all semiconductor surfaces) enabling the formation of the nanochannels of the invention, said nanochannels having a radius r as expressed by the formula as described (above) in the present invention (paragraph 47, or paragraph 129). However, the flow of chloride (e.g. HCl, or Cl₂) has to be sufficiently low in order to avoid that the etching (performed by the flow of said chloride) exceeds the germanium deposition (performed by the flow of the precursor). It is expected that the optimal flow of chloride (e.g. HCl, or Cl₂) varies with the temperature and the gasflow of the precursor.
Finding a suitable amount of chloride for use in a method according to the invention is well within the practice of those skilled in the art.
In a specific example, a silicon substrate is provided having a {100} orientation and at least one trench, said trench exposing the {100}, {110}, and {111} crystallographic planes of the silicon substrate. The width of said trench is 50 nm, the depth of said trench is 100 nm. 500 sccm GeH₄ (in 30 slm H₂ carrier gas) and 15 sccm HCl is supplied (in a CVD reactor) at 450°C and atmospheric pressure (in the CVD reactor). Epitaxial growth on the side walls alone would result in complete filling of the trench, without forming a nanopore or nanochannel. The fact that epitaxial growth occurs on the bottom and on the side walls, together with the fact that the growth at the side walls is not completely uniform from top-to-bottom, results in the formation of an embedded nanochannel, said nanochannel having a channel depth (z_c) of 50 nm and a channel width (w_c) of 10 nm.
In the present invention, a nanochannel fabrication method is described. By using selective growth of Ge in pre-etched Si trenches, under optimized growth conditions as discussed above, embedded (horizontal) nanochannels having a width of about 10 nm, 5 nm, or smaller can be obtained in the selectively grown epitaxial materials. Also arrays of nanochannels having (substantially) the same width (or diameter) can be manufactured because of the {111} facet formation. Growth conditions can be tuned to obtain smaller or larger diameters.
A manufacturing flow according to an embodiment of the method of the disclosure is schematically represented in Fig. 3.
In a first step a hardmask (2) is deposited on a substrate (1). Next, a photoresist (3) is patterned on the hardmask (2) and then, in the following step, trenches (or recessed regions) (4) are etched in the substrate (1) by e.g. dry-etch. In the following step a filling material (5) is epitaxially grown in the trenches (4) according to the method of the disclosure such that at the intersection of the growth fronts a nanochannel (6) is formed.
The formation of nanochannel is realized by controlling the growth rates of the growth fronts in a direction perpendicular to the {110} plane and, respectively the bottom {100} plane. By introducing chloride during the epitaxial growth, the {100} growth rate is reduced more than (that of) the {110} growth rate. The {111} facets (being a first pair of facets) are formed during growth as shown in Figure 2 and since the {110} planes grow fast (or grow faster compared to the {100} growth rate), another pair of {111} facets is formed before the two (opposite) {110} planes merge. After the two (opposite) {110} planes merge, a horizontal pore or channel is left in the material. By horizontal pore or channel one understands a channel having its longest dimension (length) in a horizontal direction.
The {111} facets formation is controlled by introducing chloride during epitaxial growth and by using appropriate growth conditions. The formation of {111} facets maintains the uniformity of pore diameter or width along the whole length of the nanochannel.
The epitaxial growth in the trench (or recessed region) prevents the formation of seam along the trench and embedded nanochannels are formed, as shown by the cross-section TEM shown in Figure 1(a) and 1(b).
The length of the embedded nanochannels is determined by the trench/recess region length which can be extended to microns or millimeters if needed.
Advantageously, the initial shape of the nanochannel can be modified (e.g. rounded) by a thermal treatment.
The method of the disclosure can be implemented in a high throughput and low cost manufacturing such as the ultra-large scale integration semiconductor manufacturing.
Another advantage of the different embodiments of the present disclosure is the adjustable pore length with pore lengths in the range of hundred nm up to millimeters.
The nanochannels of the disclosure can be part of or integrated with a biochip, biosensor or a micro fluidic device.
A diameter/channel width of 1 micron or smaller is obtainable with the method of the invention.
Furthermore, a diameter (or channel width) of 5 nm or smaller obtainable with the method of the disclosure, which make the nanochannels suitable for DNA separation and/or detection.
Advantageously, the surface properties of the pore/nanochannels can be adjusted to suit different applications.
With epitaxial growth, Si and Ge can be integrated to tailor the nanochannel surface properties upon the specific needs of different applications.
The nanochannel formation is determined by the crystallographic planes exposed in the recess and the epitaxy process conditions. The recess is formed (or patterned) by lithography and etching (dry or wet-etching) to have different size, profile (exposed crystallographic planes) and/or surface condition.
Advantageously, the regular nanochannels/ nanopores are formed by epitaxial growth directly in the recess, therefore no further annealing and/or chemical-mechanical processing (CMP) are needed.
Advantageously, the filling material is grown selectively only in the recess (or trench), thereby avoiding any further CMP process.
The growth rate of the growth front of the filling material in different directions, perpendicular to the crystallographic planes exposed is controlled by the amount of precursor and chlorine (or chloride) (e.g. HCl, or Cl₂) supplied as well as by the temperature and the pressure conditions of the deposition.
The shape of the nanochannel formed at the intersection of the growth fronts (or planes) can be any of the diamond-like, round, square, triangle (or rectangle, or hexagonal). Round shape can be obtained by tuning the recess profile (or design), growth conditions and/or reflow (post-treatment) process conditions.

Claims

A method for manufacturing a nanochannel device, suitable for use in biochips, biosensors or micro-fluidic devices, comprising the steps of:
- providing a mono-crystalline substrate comprising at least one recessed region, the at least one recessed region having a recess width and exposing predetermined crystallographic planes of the mono-crystalline substrate,

- epitaxially growing a filling material in the at least one recessed region,
wherein the growth rate of the growth front of the filling material in a direction perpendicular to the exposed predetermined crystallographic planes is controlled such that an embedded nanochannel is formed in said at least one recessed region at an intersection of at least two growth fronts of said filling material,
wherein the mono-crystalline substrate is a silicon substrate having a {100} orientation and at least one recessed region, said recessed region exposing the {100}, {110}, and {111} crystallographic planes of the silicon substrate, wherein the filling material is germanium and wherein the growth rate of the growth front of germanium in a direction perpendicular to the exposed {110}, {100}, and {111} crystallographic plane is controlled such that an embedded nanochannel is formed in said at least one recessed region at an intersection of said growth fronts of germanium.
The method according to claim 1, wherein said growth rate is controlled by introducing chloride during said epitaxial growth.
The method according to claim 1 or 2, wherein the width, the shape and the depth of the embedded nanochannel is determined by the recess width of the at least one recessed region and by the growth rate of the growth front of the filling material in the direction perpendicular to the exposed predetermined crystallographic planes.
The method according to any of claims 1 to 3, wherein no thermal treatment is performed prior to forming the embedded nanochannel.
The method according to any of the claims 1 to 4, wherein the epitaxial growth of the filling material is suitable to control the growth rates of the growth fronts of the filling material in different directions perpendicular to the exposed crystallographic planes, independently of each other.
The method according to any of the claims 1 to 5, wherein the width of the embedded nanochannel is lower than or equal to 1 micron, preferably lower than or equal to 10 nm.
The method according to claim 1, wherein chloride is introduced during the epitaxial growth for reducing the growth rate of the growth front of germanium in a direction perpendicular to the exposed {100} crystallographic plane more than the growth rate of the growth front of germanium in a direction perpendicular to the exposed {110} crystallographic plane, thereby forming {111} facets before two {110} crystallographic planes merge.
The method according to claim 7, wherein the formation of {111} facets maintain the uniformity of pore diameter or width along the whole length of the nanochannel.
The method according to claim 1, wherein germanium is epitaxially grown from germanium precursors such as germane, digermane, trigermane or any high order germanium precursors.
The method according to claim 1, wherein the length of the embedded nanochannel is in the range of hundred nm up to millimeters.
The method according to claim 1, wherein the mono-crystalline substrate comprises multiple recessed regions, each recessed region comprising an embedded nanochannel.
The method according to claim 11, wherein the embedded nanochannels form an array or a network of nanochannels.
The method according to claim 12, wherein the embedded nanochannels have substantially the same width.
The method according to claim 1, wherein the shape of the embedded nanochannel can be any of the diamond-like, round, square, triangle, rectangle or hexagonal.
The method according to claim 14 wherein the shape of the embedded nanochannel can be modified by thermal treatment.